MIAMI (CBSMiami) – Mitt Romney and Rick Santorum are battling it out in Michigan Tuesday as voters in the state, and in Arizona, head to the polls to pick their choice for the GOP presidential nomination. For Romney, Michigan very well may be a do-or-die state for the campaign.

Ideally for Romney, he would walk to victory in the state where he grew up and where his father was once the governor. Romney left Michigan long ago and has drawn controversy for his remarks that Detroit and the auto industry, Michigan’s life blood, should just go bankrupt.

Romney opposed the government bailout of General Motors, even though it’s proven to be a wise move on the part of the federal government as GM and Chrysler have both recovered and started hiring more American workers again.

While opposing the bailout may play well to some of the most conservative wings of the Republican Party, it’s not sitting exactly right with many Michigan voters, even GOP voters.

Still, Romney’s biggest problem in Michigan and across the country is the white, working class voter. According to new polling from the Washington Post, Romney’s favorability rating among conservative Republicans and independents who make less than $50,000 is just 37 percent.

Further, non-college white voters across the board only give Romney a favorability rating of just 37 percent. Independents are even harder on Romney giving him an approval rating of just 29 percent, compared to 44 percent who disapprove.

It’s turned Romney into the biggest question mark in the GOP nomination race. He’s got the most money, both personally and campaign-wise, but he can’t seem to close the deal and unite the party behind him.

He’s still the likely nominee based on simple math. Romney will get a portion of the delegates in Michigan, though he could get less than Santorum. Plus, he’ll take Arizona easily and take all of the delegates from that state.

The Michigan primary is an open primary, meaning independents and even Democrats can cross party lines and vote in the primary. If independents break for Santorum or split evenly between the two, it could spell big trouble for Romney going forward.

Democrats are seizing on Romney’s vulnerability in his home state. Democrats said if it took Romney millions of dollars to barely win in his home state, combined with his more hard-line right-wing talk, will alienate independent voters in the general election.